flea beetles

Hannah wrote me yesterday, “We already have flea beetles eating everyones lettuce and kale and brocoli and radish leaves. BOO! I am going to make a soap/garlic spray but I think it’s going to be futile unless everyone treats the problem. I walked around yesterday and it is afecting the same species in everyone’s plots.”

I did a brief search online and found this article. Link is at bottom.

Flea beetles are favored by stable warm spring weather and hampered by alternating periods of hot and cold temperatures with intermittent rains. Seedlings of crops are most vulnerable to flea-beetle feeding when stressed, particularly by inadequate moisture. Providing good nutrition and favorable growing conditions aids in shortening the vulnerable early-growth stages and helps plants survive flea-beetle attack. The literature suggests that organic fertilization may make crops less attractive to flea beetles. (3)

If you have fish emulsion, this might be a good time to fertilize; if you don’t have any, let me know. I have some for sale from last year.

Trap cropping, in which attractive plant species are planted near the main crop to draw the pest away, offers some possibilities for flea-beetle management. Apparently the most practical trap crop is Chinese Southern Giant Mustard (Brassica juncea var. crispifolia), seed of which is widely available. Research has shown that planting this trap crop about every 55 yards between rows of cabbage, broccoli, or cauliflower (or as a border around the field) can do an exceptional job of protecting them. To retain effectiveness, reseeding of the trap crop may be necessary, especially if the pest destroys the first planting. The trap is less effective in protecting crops that are almost as attractive to flea beetles as Giant Mustard is, such as Nappa cabbage, gai choy, and choy sum. (5)

Another approach to trap cropping is to interplant radishes—’Chinese Daikon’ and ‘Snow Belle’ are preferred by the pest—at 6- or 12-inch intervals among cole crops. In one trial, this measurably reduced damage to broccoli. (6)

Growers report some level of flea-beetle control using white and yellow sticky traps. (6, 9)
Reference is made to individual traps placed every 15 to 30 feet of row. Encircling the field with continuous sticky tape is also mentioned. Sources of sticky traps include ARBICO (10), and Golden Harvest Organics. (11)

Since the adults overwinter in plant debris, there is value in sanitation procedures that destroy refuge sites. Plowing or rototilling weeds and crop residues in the fall is often recommended, as is destruction of grassy and solanaceous (tomato family) weeds adjacent to the field. (12) Unfortunately, these procedures are often in conflict with good sustainable practices that strive to maintain soil cover and field buffers. When such conflicts occur, growers can view sanitation procedures as transitional strategies only, and look for more sustainable practices to use in the future.

This fall, we’ll have to be sure to clear out all our plots before winter.

Anecdotal reports have suggested that catnip might repel flea beetles. Research by organic gardeners in 1997 failed to confirm this information, however. The gardeners reported that catnip used as a mulch or sprayed as an extract tea did a generally poor job of repelling the pest. (13)

If you’d rather not have your vegetables competing with ornamentals for nutrition, you can always try the trap crop method to get rid of flea beetles. This method involves growing certain species of plants that are more favorable to flea beetles than the crop you’re trying to protect. Usually these are planted several feet away from your vegetables. A good example of a trap crop would be either Giant Mustard plants or Daikon Radishes).

Ensuring that your plants are getting plenty of water and nutrients will help them better resist flea beetles and avoid feeding damage. This might sound like common sense, but plants that are being stressed by a lack of water or fertilizer can be destroyed by flea beetles overnight. A good watering and fertilizing regiment can mean the difference between enjoying fresh tomatoes on a dinner salad or waking up to a row of dead tomato plants.

Food grade diatomaceous earth will help get rid of flea beetles or prevent adult flea beetles from feeding on plants. Diatomaceous earth is an incredible thing. It’s a soil composed of fossilized, microscopic algae with razor sharp edges, which are non-toxic to most mammals but fatal to insects that come into contact with it. Dusting your plants with diatomaceous earth has been shown to reduce adult flea beetle feeding to a tolerable level in areas where flea beetle populations have gotten out of hand.

Also a garlic/pepper tincture can be sprayed on the leaves. Please remember that we are a strictly organic garden. Do not use any commercial pesticide, even if it claims to be organic.

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2 thoughts on “flea beetles”

I have had good results with diatomaceous earth on soft-bodied things like cabbage worms and also for controlling weevils in stock feed. I will be interested to see whether it helps on flea beetles. (Are they soft-bodied?) If you use it, please guard against breathing it.

I also found this list of recommendations for dealing with flea beetles, most of which Keri listed above. However, it may be possible to deter them by sprinkling coffee grounds (also high in nitrogen) or chopped mint leaves around your seedlings.